In conventional automotive alternators, a rectifier and a voltage regulator are mounted to an outer end surface of a rear bracket, and a cup-shaped protective cover is mounted to the rear bracket from axially outside so as to cover the rectifier and the voltage regulator. The protective cover is supported on the rear bracket by engagement between hook portions of engaging hooks and engaging apertures by inserting engaging hooks that are disposed so as to extend axially from near an opening end of a peripheral wall portion of the cup shape into engaging apertures that have been formed on an outer peripheral edge portion of the rear bracket (see Patent Literature 1, for example).